Variable nozzle and sealing means therefor for jet engine



May '22, 1956 P. A. PITT ET AL 2,746,243

VARIABLE NOZZLE AND SEALING MEANS THEREFOR FOR JET ENGINE 5 Sheets-Sheet1 Filed Jan. 14, 1954 INVENTORS AND R A. PITT M. E.NELSON ATTORNEYS May22, 1956 P. A. PITT ET AL VARIABLE NOZZLE AND SEALING MEANS THEREFOR FORJET ENGINE 3 Sheets-Shes. 2

Filed Jan. 14, 1954 lNVENTORS 5 AND P. A. PITT M. E. NELSON I 4ATTORNEYS May 22, 1956 P. A. PITT ET AL 2,746,243

VARIABLE NOZZLE AND SEALING MEANS THEREFOR FOR JET ENGINE Filed Jan. 14,1954 5 sl'lee'lzs-shee- 5 HIGH PRESSURE HHEH INVENTORS PAUL PITT ATTRNEY5 United States Patent VARIABLE NOZZLE AND SEALING MEANS THEREFORF63 JET ENGINE Paul A. Pitt and Morris E. Nelson, San Diego, Calif., as-

signors to Solar Aircraft Company, San Diego, Calitl, a corporation ofCalifornia Application January 14, 1954, Serial No. 404,922

11 Claims. (Cl. Gil-35.6)

This invention relates to reaction engines and more particularly tonozzle mechanisms for varying the area of the exhaust orifice inturbo-jet engines.

This application is a continuation-in-part of application Serial No.59,944, filed November 13, 1948, now abandoned.

The present invention is primarily concerned with two-position nozzlesfor use with afterburner equipped engines although the invention inseveral respects is ap plicable to other types of variable nozzles. Asis well known in the art, the performance of a turbo-jet engine dependsto a large extent upon the correlation be tween the size of the exhaustorifice and the mass and velocity of the gases issuing therethrough. Ifthe opening is too large a serious loss of thrust results and if theopening is too small, the engine may overheat to the point whereexcessive deterioration or, in extreme cases, destruction of the engineresults.

The problems of nozzle control have been greatly magnified With theadvent of the afterburner which is provided to augment the mass andvelocity of the gases issuing from the primary engine. In a typical jetplane when the afterburner is cut in for a take-off, under emergencyconditions, or in a combat maneuver large quantities of additional fuelare injected into the afterburner section and in the fraction of asecond in which the afterburner ignites, the output of exhaust gasesincreases from about 2250 cubic feet per second to about 4200 cubic feetper second and in a very short time the temperature of the tailpipe mayincrease from 1200 to 1300 F. to 3000 F. or higher. These practicallyinstantaneous changes in the mass and velocity and temperature of theexhaust gases disrupt the normal operating conditions of the primaryengine, and, unless they are immediately compensated for, may result inthe loss of the aircraft and its occupants.

In recognition of these problems many prior efforts have been addressedto the problem of providing means for varying the area of the exhaustorifice of a jet engine. However, all variable nozzles known before thepresent invention have proved unsatisfactory principally because oftheir failure to operate satisfactorily under the extremely hightemperatures and pressures involved, because of their failure to observepractical weight limitations, or because the forces required to operatethe nozzle necessitate the use of impractically large and expensiveactuating mechanisms. Prior designs have also been ineffective becauseof their failure to provide for adequate cooling of the nozzlecomponents and because of their failure to provide a structure whichwill function effectively despite the distortion produced by overheatingor differential expansion.

In practice it has been found that when afterburning is initiated orshut 03 the nozzle must be moved to its new adjusted position in amatter of a second or two to prevent damage to the engine or seriousloss of thrust. When it is considered that the nozzle components are ofrelatively large size and accordingly of 2,746,243 Patented May 22, 1956"ice large mass, and if there is appreciable friction of sliding contactsurfaces, it will be appreciated that attainment of this speed ofactuation could require unduly large actuating mechanisms.

It is accordingly, the major purpose and object of the present inventionto provide improved variable area nozzles for jet engines which haveimproved structural integrity, performance and reliability in operation.

It is also an object of the invention to provide an improvedtwo-position variable area nozzle assembly in which provision is madefor cooling the movable parts to prevent distortion and binding inoperation.

It is a further object to provide an improved twoposition variable areanozzle assembly which forms a tight seal in closed position which inopen position is broken to facilitate the flow of cooling air over thetailpipe and over both sides of the movable components of the nozzle.

It is an additional object of the invention to provide improvedtwo-position variable area nozzles so constructed and arranged that theaerodynamic forces acting on the nozzle in operation permit its rapidmovement from full open to closed position and provide a cushion or stoppressure to prevent impact damage.

It is a further object to provide an improved twoposition variablenozzle having improved sealing means to prevent the leakage of hightemperature exhaust gases.

It is also an object to provide an improved variable area nozzle inwhich the movable components are entirely Withdrawn from the path of theexhaust gases during high temperature operation.

Further objects and advantages will become apparent as the descriptionproceeds in connection with the accompanying drawings in which:

Figure l is a rear end elevation of a nozzle in accordance with theinvention with a movable gate in closed position;

Figure 2 is a side elevation of the nozzle of Figure 1 taken along theline 2--2 of Figure 1 and showing the outer shroud in section andindicating the open position of the nozzle in dotted lines;

Figure 3 is a vertical sectional view taken along line 3-3 of Figure 2;

Figure 4 is a horizontal fragmentary section taken along line 44 ofFigure 2;

Figure 5 is a fragmentary vertical section taken along line 5-5 ofFigure 1;

Figures 6 and 7 are fragmentary sectional views showing details of theconstruction of the seals, the views being taken along lines 6 6 and7-7, respectively, of Figure 2;

Figure 8 is a view similar to Figure 2 showing the nozzle in openposition with the upper half in plan view and the lower half of thenozzle in section; and

Figures 9 and 10 are diagrammatic illustrations of the nozzle showingthe gates respectively in closed and open positions.

Briefly, the nozzle construction in accordance with the presentinvention comprises a fixed tubular nozzle which is sufiiciently largeto accommodate the flow of exhaust gases during afterbu'rning incombination with a pair of gates of approximately spherical curvaturewhich close over the end of the fixed nozzle to provide a nozzle openingof smaller diameter of a suitable size for accommodation of the exhaustgases during normal or nonafterburning operation. When the gates are inclosed position a seal is formed along their two longitudinal straightedges where they meet and an annular seal is formed with a stationarynozzle structure at the rear circular edges of the gates. When the gatesare in open position all of'the seals are broken to 3 facilitate theflow of cooling air over the inner and outer surface of the gates.

Referring now more specifically to the drawings indicates the tailpipeof the engine which is provided at its outlet with a slightly reducedorifice 11. The tailpipe conducts the exhaust gases from the primaryengine or from the secondary engine or afterburner if one is employedand is of sufiiciently large size to accommodate the flow of gasesduring afterburning.

Movable gates 12 and 13 are pivotally mounted as at 14 on the tailpipestructure and swing about their pivotal mountings between an openposition shown in Figure 8 and a closed position shown in full lines inFigures 1, 2, 4 and 9. In the latter position the downstream edges ofthe gates define an orifice of the proper size to accommodate the flowof exhaust gases during normal nonafterburning operation.

Each gate 12 or 13 consists of a main sheet member 15 of approximatelyspherical'curvature and an outer, correspondingly curved sheet member 16which is secured to the member 15 by bolts 17. An arcuate slot 18 isprovided in the member 16 for each bolt 17, the radius of each slotbeing centered on the pivotal axis of the gate so that the extent towhich the outer edge of the member 16 projects beyond the member 15 canbe adjusted, thereby varying the size of the nozzle aperture produced bythe closed gates. A gasket 16:: fills a corrugation 16b in the member 16and effects a seal between the members 15 and 16.

Each of the members 15 is secured at each of its opposite side edges toa hinge member 19 (Figures 2 and 7), as by spot welding indicated at190. The upper and lower hinge members 19 on each side have overlappingcars 19:: that are hingedly connected together by the pivot pins 14 thatextend through apertures provided therefor in the ears 1%. Thus as shownin Figure 4 the pin 14 may be in the form of a screw threaded into aboss 29 on a bracket plate 21 that is removably secured by bolts 22 to abracket plate 23 that'is welded to an annular supporting rib 24 ofchannel section which encircles the tube 10 and is secured thereto bytangential straps 61) positioned within the channel of the rib andwelded at one end to the rib and at the other end to the tube 11)(Figure 3).

To open and close the gates 12 and 13, a rear extension 19]) on each ofthe hinge members 19 is pivotally connected to a link 26 and the otherends of the links 26 are pivotally connected to the rear end of anactuating rod 27. provided with a clevis 27a which clevis encloses eyes26a on the ends of the links 26. The eyes 26a are connected to theclevis 27a by a pin 2? which pin extends beyond the clevis at each endand supports a pair of guide rollers 30. These guide rollers 30 roll ina tunnel 31 of rectangular cross section, into which the rods 27 extend,the tunnel having slots 31a in its upper and lower sides, through whichthe links 26 project. The rear end of the tunnel 31 is connected by apin 32 to the bracket 21 previously mentioned, and the forward end oftunnel 31 is connected by pins 33 to brackets 34 that are welded to theouter surface of the tube It}. It will be apparent from the foregoingdescription that forward movement of the control rods 27 (there is oneon each side of the tube 10) moves the connected ends of the two links26 forwardly to swing the hinge members 13 and the gates 12 and 13connected thereto into the open position shown in Figure 8. On the otherhand, rearward movement of the rod 27 moves the gates 12 and 13 into theclosed position shown in full lines in Figure 2, and asthe gates reachclosed position, the

links 26 constitute a toggle mechanism to provide a powerful closingforce on the gates. As shown in Figure 2, in the closed position of thegates the inner end of links 26 supported on pin 29 are carried'beyondthe point of alignment with the outer ends of the links to lock thegates in closed position despite breakage of rod 27 or loss of actuatingpressure thus providing a fail safe condition.

Referring to Figure 4, the rear end of the rod 27 is 4 The overtravel ofthe inner end of the links 26 has been exaggerated in Figure 2 forclarity.

When the gates 12 and 13 are in closed position the members 15 thereofseal with the main nozzle tube 10 as shown in Figure 5. Thus the tube 10has welded thereto an annular member of L-shaped cross section, oneflange 34 of which extends radially outward from the tube 10, and theother flange 35 of which lies against and is welded to the tube 10. Theradial flange 34 is reinforced by an extension 36 of the orifice member11, which is welded to the radial flange 34 near its outer edge asindicated at 37. The seal between the member 15 and the flange 34 iseffected by a corrugated bellows 38 which is bolted at its front edge tothe member 15 by bolts or screws 39 which extend through the member 15and into an inner reinforcing ring 41 which lies against the thinbellows member 33. At its rear end, the bellows 38 is provided with agasket 42 of some resilient, heat resisting material which gasket bearsagainst the radial flange 34 when the gates are in closed position asshown in Figure 5.

When the gates are in open position as shown in Figures 8 and 10 theseal formed between the gasket 42 and the flange 34 is broken so thatcooling air may flow between the gates and the tailpipe as well as overthe outer surface of the gates, as will be more fully explained.

When the gates 12 and 13 are in closed position, the upper side edges ofthe lower gate 12 abut against the lower side edges of the gate 13 overmost of the areas of those edges, and to provide a seal therebetween,flexible sealing strips 45 are provided which abut against each otherwhen the gates are in closed position, as shown in Figure 6. Theseresilient sealing strips 45 are. secured, as by welding 46 adjacenttheir outer edges, to outwardly extending flanges 47 on the hingemembers 19. The sealing leaves 45 are urged into sealing contact witheach other, not only because of their natural resiliency, but by anypressure existing within the nozzle.

Adjacent their rear ends, the flanges 47 on the hinge members 19 abutagainst one of two plates 50, which extend diametrically from oppositesides of the tube 10 just back of the radial-flange 34. These platesassure that when the nozzle is closed the two gates 12 and 13 aresymmetrically positioned with respect to the axis of the The gatesections 12 and 13 and the associated seals possess sufiicientresiliency to maintain a tight seal despite the slight overtravel of theinner ends of the toggle links 26 to provide the fail safe conditiondescribed above.

The main tube 10 and the nozzle structure that has been described areenclosed in an outer tubular shroud 53 that is spaced from the innerstructure so as to permit the circulation of cooling air therethroughand constitute a cooling shroud and radiation shield. The forward end ofthis shroud 53 (not shown) is open, and the rear end is open andprojects beyond the orifice 11 and the ends of the gates 12 and 13. Therush of exhaust gas through the nozzle and the rear end of the shroud 53induces a draft of air therethrough that functions to cool the parts. inaddition, when the gates 12 and 13 are in their fully open positionthere is a clearance between the gates and the tube 10 which allows aportion of the cooling air passing through the shroud to be drawn underthe gates to insure cooling of the most critical areas directly adjacentthe end of the tube. These areas are critical since the distortiontendencies of the adjacent parts are greatly increased unlesstemperatures can be kept reasonably low. Itis important to note herethat the feature which allows cooling air to be drawn under the gates 12and. 13 in their open position is a very necessary one from a practicalstandpoint since cooling air requirements are very much greater duringafterburning than during the normal or no-burning operation. Duringafterburning the 3000F.

greases temperature of the gases would quickly melt the nozzle orificeif it were not cooled. Thus, the two-position nozzle embodied hereinallows for naximum air pumping action during afterburning when the gatesare open, and a reduced air flow which remains substantiallyproportional to the cooling or heat rejection requirementsduring normaloperation when the gates are closed.

The flow of cooling air and the pressure areas during nonafterburningand afterburning conditions when the nozzle is, respectively, closed andopen are illustrated in Figures 9 and 10. In Figure 9 the high pressurearea is shaded. it will be seen from Figure 9 that the pressure withinthe gates is higher than that of the air surrounding the gates. Thus ifit were not for the flexible seal formed by the packing 42 and theflange 34 the gases would flow between the gates 12 and 13 and the endof the tailpipe 10 toward the left as viewed in Figure 9. Leakage atthis point, which is effectively prevented by the sealing arrangementabove described, would result in a serious loss of thrust and wouldexpose additional portions of the nozzle mechanism to the action of thehigh temperature exhaust gases.

in the open position it will be seen from Figure 10 that the packing 42separates from the flange 34 and because of the aspirating effect of thegases flowing through nozzle 11 a flow of cooling air is induced betweenthe tailpipe and the respective gates 12 and 13 as well as between thegates and the outer shroud. Thus, a flow of cooling air over the mostcritical areas directly adjacent the end of the tailpipe is insuredwhich is greatest when cooling requirements are at a maximum. It shouldbe noted that cooling of the gates in the open position is also effectedby removing the gates from the path of the high temperature gas asopposed to many of the prior art devices. Excessive pressure forces onthe gates when they occupy the retracted position are thus eliminated.In prior structures in which this is not accomplished these forces whichare of considerable magnitude are transmitted to the supporting tailpipewhich is operating at temperatures which reduce the material strength toa fraction of its room temperature strength. The present inventionbecause of the provision of ample cooling of the entire nozzle assemblyand tailpipe during afterburning and by the removal of the movable gateelements from the path of the exhaust gases provides a nozzle assemblywhich has longer service life, may be lighter in weight and is ofgreater reliability than presently known structures of this type.

As stated above, it is of primary importance that the nozzle be capableof extremely rapid actuation. For example, it should move through itsrange of movement in one second or less and this should be accomplishedby the use of actuating mechanisms of minimum size. The attainment ofthese results for the first time in the art is an important feature ofthe present invention.

As pointed out above the movable gate assemblies are substantiallyhemispherical in shape. Accordingly the gas pressure forces actingnormal to their surfaces will pass through the center of curvature lyingon a line between the two hinge points. The resulting vector forces arethus resolved into a radial force passing through the center of thehinge point regardless of the position of the gate. Thus the gates aresubstantially in balance with respect to the pressure forces acting onthem in all positions and an actuating force of minimum value is thusrequired to move the gates in either direction between open and closedpositions.

Tests under actual operating conditions have demonstrated that due tothe substantial balance of the major pressure forces the nozzle may bemoved between full open and closed positions within one second with theuse of small light weight actuating mechanisms and without impact damageto the gates when they reached closed position.

There are, however, several unbalanced forces acting on the gates whichare used to advantage in the operation of the gates. First there is arelatively small aerodynamic force due to the passage of gases over thecurved lips of the segments 16 which tends to swing the nozzle towardsclosed position. However, in the absence of any actuating force, thenozzle will be held in balance in a slightly open position because oftwo additional counter-forces. One of these is the sum of gas pressureloads that act over the area of the bellows 38 on the inner periphery ofthe gates. Another is the spring force resulting from the compression ofthe bellows 38 and side seals when the gates approach the fully closedposition. Both of these latter forces oppose and balance the lightaerodynamic closing force within the last five or ten degrees of travel.The internal pressure forces which efiectively act over the area of thebellows seal are shown by the shaded area in Figure 9.

It will be appreciated that the novel toggle action of the controlmechanism when the nozzle is in the closed position gives assurance thatthe nozzle will remain closed even though the hydraulic system should bemade inoperative. For example, in combat, should the hydraulic system ofthe nozzle actuator be disrupted, the forces acting against the innersurfaces of the gates will maintain the gates in closed position becauseof the toggle construction. In the absence of the toggle lock, the jetforces would move the gates radially outwardly to a semi-open positioncausing substantial thrust loss. Therefore, it should be understood thatthe toggle lock in the nozzle closed position is an important part ofthe invention.

Should the actuating system fail, the afterburning in progress and withthe nozzle in the open position, the gates would tend to move toward theclosed position because of the aerodynamic force produced by the passageof gases over the curved lips of the segments 16. However, under suchconditions the pilot would immediately stop afterburning, the gateswould assume the semi-closed position described above, and the powerplant would have sufiicient thrust to allow a considerable amount ofuseful flying time.

From the foregoing it will be seen that the abovestated objects of theinvention have been accomplished by the provision of an improvedtwo-position nozzle assembly which is of lightweight construction,susceptible of rapid actuation with relatively low actuating forces andwhich is adequately cooled during high temperature operation and thushas an extended service life.

The invention may be embodied in other specific forms Without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A variable nozzle construction for a jet engine exhaust dischargecomprising a tailpipe for conducting the exhaust stream and having afixed discharge orifice; a pair of movable gate members disposedexternally on opposite ides of said tailpipe adjacent its dischargeorifice and shaped so as to form a sealed annular tailpipe extensionWith a reduced discharge orifice when positioned in a closed positionwith oppositely disposed mating portions in engagement; an annularexterior shoulder on said tailpipe; internal shoulders on said gatemembers for forming with said exterior shoulder a substantially annulargas tight seal when the gate members are in closed position; andmechanism for simultaneously shifting both gate members to a retractedposition clear of the exhaust gases issuing from said fixed dischargeorifice and with the respective shoulders on said gate members and saidtailpipe in clearance relation to form a cooling air passagetherebetween. V

e 2. A nozzle construction according to claim 1 in which said internalshoulders on said gates each comprise a corrugated bellows secured atone edge to the gate and having at its other edge a gasket adapted toseal against the annular shoulder on said tailpipe.

3. A variable orifice nozzle construction for jet engine exhaustdischarges comprising a tailpipe having a fixed discharge orifice forconducting the exhaust stream; a pair of movable gate members disposedexternally on opposite sides of said tailpipe adjacent its dischargeorifice and shaped so as to form a sealed annular tailpipe ex-.

tension with a reduced orifice when positioned in a closed position withoppositely mating portions in engagement; outwardly extending flanges onsaid gate members adjacent said mating portions and adapted. to closelyapproach each other in an axial plane of said tailpipe when the gatesare in closed position; mating resilient sealing means on said flangesfor sealing them with respect to each other when said gates are inclosed position; additional sealing means mounted on said gate membersand said tailpipe effective to maintain a seal therebetween only in theclosed position of said gate members; and mechanism for shifting bothgate members to a retracted position clear of the exhaust gases issuingfrom said fixed discharge orifice and to break said last mentioned sealto permit the passage of cooling air therethrough.

4. A nozzle construction according to claim 3 in which said sealingmeans on said flanges comprises elastic strips secured at their outeredges to said flanges and extending inwardly and away from said flangesinto contact with each other when the gate members are in closedposition.

5. A variable orifice nozzle construction for jet engine exhaustdischarges comprising a tailpipe having a fixed discharge orifice forconducting the exhaust stream; a pair of movable gate members disposedexternally on opposite sides of said tailpipe adjacent said dischargeorifice and shaped so as to form a tailpipe extension with a reducedorifice when positioned in a closed position with oppositely matingportions in engagement; outwardly extending flanges on said gate membersadjacent said mating portions and adapted to closely approach each otherin an axial plane of said tailpipe when the gate members are in closedposition; mating sealing means on said flanges for sealing them withrespect to each other when said gate members are in closed positioncomprising elastic strips secured at their outer edges to said flangesand extending inwardly and away from said flanges into contact with eachother when the gate members are in closed position; additional sealingmeans including diametrically outwardly extending flanges on saidtailpipe adapted to be engaged between said outwardly extending flangeson said gate members forward of said sealing means when said gatemembers are in closed position; and mechanism for shifting both gatemembers to a retracted position clear of the exhaust gases issuing fromsaid fixed discharge orifice.

6. A variable orifice nozzle construction for jet engine exhaustdischarge comprising a tailpipe having a fixed discharge orifice forconducting the exhaust gas stream; a pair of movable gate members eachcomprising overlapping front and rear plates disposed externally onopposite sides of said tailpipe adjacent the discharge orifice shaped soas to form a sealed annular tailpipe extension with a reduced orificewhen in a closed position; oppositely disposed mating sealing portionson said front plates adapted to sealingly engage when said gate membersare in closed position; means securing said rear plates to the frontplates for relative adjustable sliding move ment with respect theretowhereby the size of the orifice defined by the gate members in closedposition can be varied; and mechanism for shifting both gate members toa retracted position clear of the exhaust gases issuing from said fixeddischarge orifice, said gate members being spaced from said tailpipewhen the members are in retracted position to form a cooling air passagebetween said gate members and said tailpipe.

7. A variable orifice nozzle construction for jet engine exhaustdischarge comprising a tailpipe for conducting the exhaust stream andhaving a fixed discharge orifice; a pair of movable gate membersdisposed externally'on opposite sides of said tailpipe adjacent itsdischarge orifice and shaped so as to form a sealed annular tailpipeextension with a reduced discharge orifice when positioned in a closedposition; oppositely disposed mating sealing members on said gatemembers adapted to be sealingly engaged in said closed position of saidgate members; cooperating sealing means on said tailpipe and said gatemembers to maintain a substantially annular seal therebetween only insaid closed position of said gate members; mechanism for shifting bothgate members to a retracted position clear of said tailpipe dischargeorifice and to separate said cooperating sealing means to form a coolingair passage between said gate members and said tailpipe when the gatemembers are in retracted position; and a cooling air shroud surroundingsaid tailpipe and gate members in the region of said shifting mechanismfor supplying air to said cooling air passage to cool said gate members,said tailpipe and shifting means and to heat shield the enclosurenormally housing the exhaust pipe.

8. A variable orifice nozzle construction for jet engine exhaustdischarge comprising a tailpipe for conducting the exhaust stream andhaving a fixed discharge orifice; a pair of movable gate membersdisposed externally on opposite sides of said tailpipe adjacent itsdischarge orifice and shaped so as to form a sealed annular tailpipeex-' tension with a reduced discharge orifice when positioned in aclosed position with oppositely disposed mating portions in engagement;mechanism for shifting both gate members to a retracted positionradially spaced from said tailpipe to form a cooling air passagetherewith and clear of the exhaust gases issuing from said fixeddischarge orifice; sealing structure on said tailpipe and said gatemembers effective to seal said gate members with each other and withsaid tailpipe when said gate members are in closed position; saidsealing structure including relatively movable members which areseparated in the retracted position of said gate members to form acooling air passage between said gate members and said tailpipe.

9. The construction as defined in claim 8 in which at least a portion ofsaid sealing structure is responsive to exhaust gas pressure to increasethe sealing pressure when said gate members are in closed position.

10. In a variable discharge orifice construction for combustion engineexhaust gases; a tailpipe having a fixed discharge orifice; a pair ofgate members of generally semi-spherical shape; hinge structurepivotally supporting said gate members on opposite sides of saidtailpipe adjacent its orifice for swinging movement between an openposition in which said gate members are clear of said tailpipe dischargeorifice and a closed position in which the gate members constitutetailpipe extensions forming a discharge orifice of reduced size; anexternal annular shoulder on said tailpipe forward of the said dischargeorifice; internal semi-circular shoulders on said gate membersconstituting an annular shoulder forward of said external shoulder whensaid gate members are in closed position; and sealing means atfixed toone of said annular shoulders and facing the other of said annularshoulders for effecting a gas-tight seal between said annular shouldersonly when said gate members are in closed position, said seal beingbroken to form a cooling air passage between said gate members and saidtailpipe when said gate members are in open position.

ll. A variable orifice nozzle construction for jet engine exhaustdischarges comprising a tail pipe having a fixed dischargeorifice forconducting the exhaust stream; a

pair of movable gate members disposed externally on opposite sides ofsaid tail pipe adjacent said discharge orifice and shaped so as to forma tail pipe extension with a reduced orifice when positioned in a closedposition with oppositely mating portions in engagement; outwardlyextending flanges on said gate members adjacent said mating portions andadapted to closely approach each other in an axial plane of said tailpipe when the gate members are in closed position; mating sealing meanson said flanges for sealing them with respect to each other when saidgate members are in closed position comprising elastic strips secured attheir outer edges to said flanges and extending inwardly and away fromsaid flanges into contact with each other when the gate members are inclosed position; additional sealing means including diametricallyoutwardly extending flanges on said tail pipe adapted to be engagedbetween said outwardly extending flanges on said gate members forward ofsaid sealing means when said gate members are in closed position; andmechanism for shifting both gate members to a retracted position clearof the exhaust gases issuing from said fixed discharge orifice.

References Cited in the file of this patent UNITED STATES PATENTS MeyerFeb. 18, Dennis June 8, Humphris Mar. 29, Goddard Apr. 9, Odin Nov. 9,Neal Sept. 6, Oulianofl Sept. 26, Haltenberger May 1, Brown July 15,Ambrose et al. Apr. 21, Laucher May 12,

FOREIGN PATENTS Germany June 5, Great Britain Nov. 24, Great BritainMar. 24, Great Britain Mar. 24, Great Britain Apr. 29, Great Britain May27,

